[apm] adding env tag to configuration.
diff --git a/manifests/init.pp b/manifests/init.pp
index 4a1531e..da94cce 100644
--- a/manifests/init.pp
+++ b/manifests/init.pp
@@ -154,6 +154,9 @@
 #   $apm_enabled
 #       Boolean to enable or disable the trace agent
 #       Boolean. Default: false
+#   $apm_env
+#       String defining the environment for the APM traces
+#       String. Default: empty
 #
 # Actions:
 #
@@ -241,6 +244,7 @@
   $dd_user = $datadog_agent::params::dd_user,
   $dd_group = $datadog_agent::params::dd_group,
   $apm_enabled = false,
+  $apm_env = '',
 ) inherits datadog_agent::params {
 
   validate_string($dd_url)
@@ -302,6 +306,7 @@
   validate_bool($sd_jmx_enable)
   validate_string($consul_token)
   validate_bool($apm_enabled)
+  validate_string($apm_env)
 
   if $hiera_tags {
     $local_tags = hiera_array('datadog_agent::tags')
diff --git a/spec/classes/datadog_agent_spec.rb b/spec/classes/datadog_agent_spec.rb
index b4225f0..5ffd0cd 100644
--- a/spec/classes/datadog_agent_spec.rb
+++ b/spec/classes/datadog_agent_spec.rb
@@ -512,6 +512,21 @@
                     'content' => /^apm_enabled: true\n/,
                 )}
             end
+            context 'with apm_enabled set to true and env specified' do
+                let(:params) {
+                    {:apm_enabled  => true,
+                     :apm_env => 'foo',
+                }}
+                it { should contain_file('/etc/dd-agent/datadog.conf').with(
+                    'content' => /^apm_enabled: true\n/,
+                )}
+                it { should contain_file('/etc/dd-agent/datadog.conf').with(
+                    'content' => /^\[trace.agent\]\n/,
+                )}
+                it { should contain_file('/etc/dd-agent/datadog.conf').with(
+                    'content' => /^env: foo\n/,
+                )}
+            end
             context 'with service_discovery enabled' do
                 let(:params) {
                     {:service_discovery_backend  => 'docker',
diff --git a/templates/datadog.conf.erb b/templates/datadog.conf.erb
index 607d511..dfb26c4 100644
--- a/templates/datadog.conf.erb
+++ b/templates/datadog.conf.erb
@@ -414,3 +414,8 @@
 # ========================================================================== #
 
 <% end -%>
+
+<% if not @apm_env.empty? -%>
+[trace.agent]
+env = <%= @apm_env %>
+<% end -%>